Any idea why my Noise Margin would suddenly leap up?

[PuncH]

from 16.3 to 18.3?

It's usually around 12 but a couple of re-syncs just before Christmas put paid to that. It's been stable now for 3 days, but the NM just shot up (without a re-sync).

[Rik]

There's less noise around during the day, Jonathan, so if your last resync was at night, I'd expect to see a higher margin during the day.

[PuncH]

Would it be a good idea to force a re-sync whilst the margin is so high? Or would it give me a slower sync speed? I always thought a high noise margin was bad.

[Rik]

You'll get a higher sync speed if you resync now, because you have the extra headroom over your target margin.

[PuncH]

OK...I'll give it a whirl.

[Rik]

Bear in mind that, before Max, the greater the noise margin the better. High margins are not, in themselves bad, what matters is the target margin, that restricts the speed at which you can sync. If you see your margin go above that, you can force a higher speed, but the downside is that the line is likely to be less stable, particularly at night, when noise levels rise.

[PuncH]

Nope...'tis the same sadly.

Something has messed up my connection a little bit somewhere and I have no idea what it is, but I'm now sync'ing approx 3000kBps slower than about a week or so ago.

[Rik]

What are your router stats, and what were they a week ago?

[PuncH]

Port Status TxPkts RxPkts Collisions Tx B/s Rx B/s Up Time
WAN PPPoA 1264 1533 0 122 450 00:41:25
LAN 10M/100M 1460 0 0 106 0 00:42:33
WLAN 11M/54M 3201 2918 0 620 230 00:42:24


ADSL Link Downstream Upstream
Connection Speed 14335 kbps 888 kbps
Line Attenuation 15.0 db 6.2 db
Noise Margin 18.3 db 10.9 db

only difference between now and a week ago is the higher noise margin (was about 12dB) and lower sync speed (usually around 17500)

I'm wondering if it's the small change support made to my line when the peterborough thing happened. support put me on a "super stable" profile, to see if that would help. of course, it didn't because peterborough was the problem. i might call support on the 4th and see if they can change my profile back to what it was because it used to stay up for weeks/months at a time!

[Rik]

The 3db and the stability profile will have hit your sync speed, Jonathan. Give support a call on Monday and they can tweak some more.

[PuncH]

Now the noise margin has gone up to 24dB and the sync speed is 10900!

Had a re-sync 25 mins ago but routerstats wasn't running.

[PuncH]

Just checked my routers logs and there was just the one re-sync in 48 hours, and it's cost me 6dB on my noise margin! Is the stability profile I'm on really over the top by any chance?

[Rik]

Not necessarily, if you're still re-syncing, Jonathan.

[PuncH]

Is there anything I can try myself before I call support next week? New adsl cable? filter?

[Rik]

It's always worth eliminating any possible cable and filter issues, preferably trying the router in the test socket if you have an NTE5 face plate. Check that you have no ring wires connected (terminal 3) and if none of that helps, run the MW radio test. For this, you need a battery powered MW radion, which should be de-tuned so you only have white noise. Use that to follow the wiring from entry point to router, pay particular attention to the router power supply, the monitor and the CPU PSU. If the noise increases at any point, that's a likely source of interference.

[PuncH]

Switched off router this afternoon for a couple of hours, and before I switched it back on again I changed the adsl cable.

Now sync'd at 9727 and 26.8dB noise margin. This is getting silly now. My connection is almost half the speed it was just before Christmas and the problem with the Peterborough BRAS 

[Rik]

What sort of ADSL cable are you using, Jonathan, flat or round?

[PuncH]

It is a flat one admittedly, as that's all I have. But it's only about 4ft long.

[Rik]

Round is better if you can pick one up. Look for the Belkin shielded cable.

[PuncH]

Will do. I just don't understand how a completely stable and fast connection can go to pot like this. Could it be something wrong at my exchange?

[Rik]

It could, or the node, Jonathan. The cable, though, will just give you the best chance. Consider yourself lucky, anyway. My line has been down since December 26. BT swear that there's nothing wrong and it's in sync, but as it doesn't have a router connected, I suspect they are missing something.

[Sebby]

These cables are decent:

http://www.adslnation.com/phpapps/catalog/index.php?cPath=21

[PuncH]

Hi guys,

Thanks for your continued responses and advice.

Rik...could the problems at the Peterborough BRAS (assuming they are ongoing) cause me to lose sync? I always thought it meant there was a problem between my router and the exchange when I lost sync.

Sebby...cheers for the link. Will try a new cable and filter from there, expecially if the problems persist.

[Rik]

Node problems shouldn't cause a loss of sync, that's generally local noise or an exchange fault. As this is BT, however, never say never.

[PuncH]

Rik...do you think my current sync speed issues could be linked with the ongoing farce at Peterborough?

[Rik]

It has to be possible, Jonathan. Until BT tell us what the fault is, exactly, no-one can be sure.

[PuncH]

Well, after a lovely evening of full internet access following the apparent "fix" of the Peterborough issue my line briefly dropped again this morning.

I didn't see the big increase in noise margin this time, which was nice but I took the oppotunity to try the BT test socket.

I get exactly the same sync speed and noise margin using the test socket, so does that rule out any of my equipment being faulty inside my house? (ie...router)

[Rik]

Yes.

[PuncH]

Yes.

Whoopee!

Once my new filter and shielded twisted pair ADSL cable arrives from ADSLNation I shall swap back onto the normal socket and then see how things go. Support have said they can get my line retrained so hopefully I'll get back to where I was speedwise just before all this trouble started. If not, then there must be a small problem on my line somewhere.

You know, I'm sure I heard some crosstalk when I was on the phone the other night 

[Rik]

 

[PuncH]

Posty has just been and delivered my ADSL Nation goodies, so they are now installed.

Fingers crossed for when IDNet reset my profile and take off super stable! 

[PuncH]

Instant improvement on the upstream noisemargin. It was 10.x db this morning and had a sync of 888kbps.

ADSL Link             Downstream  Upstream
Connection Speed  9727 kbps    1244 kbps
Line Attenuation    15.5 db        6.2 db
Noise Margin          24.3 db       6.5 db

Would I be wrong to be hopefull of regaining my old speeds of 17500 downstream once my profile is reset?

[Glenn]

 

[Simon_idnet]

Hi PuncH

Your Profile is dependent upon the Connection Speed which is dependent upon the Noise Margin. If the Exchange sees that the interference on your line has reduced then it will reduce your Noise Margin back down towards the target 6dB. As the Noise Margin reduces then there are more available frequencies for your router to use for bandwidth and so your Connection Rate will increase. If your Connection rate increases then so will your Profile which will then provide you with a higher throughput.

Regards
Simon

[PuncH]

I switched my router off last night in an effort to help things out...bad idea.

Now connected at 5200 with a noise margin of 30!

Been on the phone to Miriam this morning who has said to wait till the Peterborough BRAS issue is properly sorted, and then they will look at my line because it's likely all the ups and downs/dropouts etc over the last 3-4 weeks have not helped at all.

[Steve]

You could well have ended up with your profile being banded by BT due to the  Peterborough issues and the noise margin of 30 now shows the potential for future gains after  they've sort it out.

These are taken from the plusnet forum, So if interleaving and an increase in your target SNR doesn't stabilise the line the DLM will band your profile so you sync within certain limits

WBC banded line profile (rate kbps)
7168 - 14336
4864 - 9728
3328 - 6656
2272 - 4544
1472 - 3072
1152 - 2272
576 - 1152
288 - 576
160 - 288

[PuncH]

I've been seeing daily re-syncs, just once, in the morning since the Peterborough thing started and these re-syncs are what has killed my speed.

Would I be right in thinking the re-syncs are a response to the previous nights ups and downs etc? I've just realised they did stop for 3 or 4 days around Christmas which is also when there were no issues with the Peterborough BRAS.

If so, I look forward to the day BT fix the damn thing!

[Rik]

It's hard to say, Jonathan, but it's a possibility.